Bob,
I need a better idea for twisting triangle wire that has a
tapering end.
You’ve set yourself a difficult puzzle.
No doubt you can make one or two, or many, so long as you don’t mind
taking the time and effort to tweak and adjust, and to scrap some
that don’t work.
But when you say you need many,
There’s only one really easy answer to this.
Industrially, someone would make a proper die, a die striking or
perhaps a swaging die, that could product this form. Lots of money to
do that, but once you have the die, and the press or swaging machine
to use it in, you could bang em out.
However, that’s unlikely to be reasonable for you.
So.
Make one perfect sample. Take however long it takes to get it there
Note that a twisted triangle wire, once twisted, is round. The
triangle wire means the grooves in the twist are deeper than a square
wire would give, and the cross section tells you how many ridges or
threads are going around the wire.
But you could, if you needed, produce the form literally by cutting
it into a round taper with a file. Slow, but possible. Using the
threading fixtures on appropriate machine lathes could also do this
in the unlikely event you could figure out how to hold the gold twist
wire centered and rigidly enough in a lathe. If it was larger, you
could do both the twist and the taper with the same cut. But again,
in a smaller gold wire, this might be a very difficult cut with even
the best machine lathes. A grinder, rather than a lathe tool, such
as might be used industrially to make small milling cutters or drills
might also be an inspiration as to how to cut these.
And on that thought, As a model, for some “speeds” of twist, you
might even be able to find an existing cutting tool to use as the
sample. I’m thinking of tapered spiral milling cutters like those
used in CAD/CAM milling machines to cut wax models. These are also
sometimes a spiral triangle form, available in different degrees of
taper. Most that I’ve seen though, don’t have as fast a spiral twist
as your photo.
Anyway, however you make the single perfect sample, make it perhaps
five or ten percent oversize. (whatever is needed to adjust for
casting shrinkage)
Then make a good rubber mold, or better, have a metal mold made. The
idea is to be able to get really high quality wax models with a
minimum mold mark.
Then cast them. This will be more efficient in terms of gold use,
much more efficient in terms of time, and will solve the whole puzzle
of how to actually fabricate these repeatably and efficiently. With
14K gold, choose the right alloy, and with centrifugal casting
(allows lower flask temps, which gives a finer grain structure), you
then can heat treat to get a degree of hardness/springyness if you
need it, and you should be able to get pretty close to the
metalurgical properties of what you’d get if you fabricate these.
Not exact, but perhaps close enough…
Now that I’ve written all that, (which I won’t bother to delete
because it may still be the best answer if you need many) I’ve got
another idea that just occured to me as I type…
Take a pair of decent round nose pliers (yes, round nose. That
allows the spiral to be gripped without creating a flat in the long
dimension. On one jaw, file one or more triangle grooves, following
the round jaw profile. The triangle grooves should be not only
following around the jaw of the plier, but also angled to roughly the
desired speed of the spiral. If you get this right, you’ve got a
plier that can grip the spiral at any point along it’s length before
or after twisting, without leaving an ugly scar or plier mark. You’ll
want to polish those holding portions of the plier jaws for the same
reason. You might have to play with that angle a bit to get it to
work, since it also has to grip the wire before it’s twisted. And you
might need a couple grooves of varying depth to grip the taper well
as it gets smaller but also at it’s larger dimentions.
I’m kind of imagining that the groove you first use to grip the wire
could be straight. But you’d need the angled grooves to then go back,
if needed, and adjust and tweak the twist after the initial twisting.
Perhaps a “hybrid” groove in the plier jaw could do both… (forgive
me if this seems muddled. I’m kinda trying to think it through as I
type. Doesn’t make for a great description)
You also need a second such fitted plier, but this one cut in
flat/needle nose pliers with the groove straight and flat and not
angled, to hold the untwisted part of the wire, while the other plier
is doing the twisting. Also polished…
To use this, you’d firmly grip with the modified flat/needle nose
plier, while the other started at the large end and gradually slid
down the taper while twisting. This would take a bit of practice, but
should work. The twisting would be taking place mostly right next to
the round nose plier, since the metal there is thinner, while as you
slide that plier towards the end (while twisting), the thicker
tapered portion, being both thicker and now already a bit work
hardened, shouldn’t twist too much more. So how much you twist is a
balance between how fast you twist and how fast you slide the round
nose plier down the wire…
Hope that gives you some ideas…
Peter Rowe